When taking an inventory of forests, borders in the form of boundary lines are determined in order to limit a region within which the inventory work, with respect to the amount of timber and possibly also type of timber, is to take place.
Coordinate points are set out, in order to determine the locations of the boundary lines. When such a point has been found, the position of the subsequent coordinate point must be determined. This takes place through an operator being present at one coordinate point and determining with the aid of a map the direction and distance to the subsequent coordinate point. One person stands at the first coordinate point with an instrument that comprises a compass and a laser pointer. A second person is located in the vicinity of the second coordinate point. The latter person may wear, for example, a high-visibility jacket to ensure high visibility. When the laser beam impinges on the jacket in what is, according to the map, the right direction, the position of the boundary line can be determined and labelled.
The said instrument is prior art technology, and comprises a compass housing with a cover that extends from the upper surface of the compass rose inside the compass housing and downwards parallel to the axis of rotation of the compass. The cover is provided with a scale of 360 degrees or 400 degrees. The compass housing is attached to the housing of the instrument. The cover can be observed through a slit outside of the compass housing, whereby the direction of the compass can be read as a number of degrees.
A green laser is mounted in the housing of the instrument parallel to the direction of the compass, such that when the compass specifies a certain direction a laser beam is projected in the specified direction.
The instrument is used as follows: an operator looks through the said slit with one eye and observes where the laser beam impinges onto an object with the second eye.
The instrument is portable and is not significantly larger than a normal compass.
In order to stake out boundary lines, therefore, it is required that two people gain access to a region of forest, that may, in many cases, be difficult to access.
A major problem with the instrument described is that gas bubbles tend to form in the compass housing. This is normally a consequence of the instrument being exposed to variations in temperature. When bubbles form inside the compass housing, it may no longer be possible to read the scale on the cover with sufficient accuracy to specify the correct compass direction.
In order to correct this, the instrument must be taken to a workshop for the compass housing to be exchanged. In addition to a loss of time, this involves also an unwelcome interruption in the measurements that were to be carried out.
The present invention solves this problem.